Mirim Lagoon Research Articles

A Software Tool for ICESat and ICESat-2 Laser Altimetry Data Processing, Analysis, and Visualization: Description, Features, and Usage

This paper presents a web-based software tool designed to process, analyze, and visualize satellite laser altimetry data, specifically from the Ice, Cloud, and land Elevation Satellite (ICESat) mission, which collected data from 2003 to 2009, and ICESat-2, which was launched in 2018 and is currently operational. These data are crucial for studying and understanding changes in Earth’s surface and cryosphere, offering unprecedented accuracy in quantifying such changes. The software tool ICEComb provides the capability to access the available data from both missions, interactively visualize it on a geographic map, locally store the data records, and process, analyze, and explore the data in a detailed, meaningful, and efficient manner. This creates a user-friendly online platform for the analysis, exploration, and interpretation of satellite laser altimetry data. ICEComb was developed using well-known and well-documented technologies, simplifying the addition of new functionalities and extending its applicability to support data from different satellite laser altimetry missions. The tool’s use is illustrated throughout the text by its application to ICESat and ICESat-2 laser altimetry measurements over the Mirim Lagoon region in southern Brazil and Uruguay, which is part of the world’s largest complex of shallow-water coastal lagoons.

The use of integrative tools and multiple models for aquatic environmental quality assessment: a case study of the Mirim Lagoon, Southern Brazil.

This study performed toxicity assays with microalgae, microcrustaceans, and fish as well as evaluated biochemical and behavioral biomarkers in fish and microcrustaceans to assess the quality of the surface water of Mirim Lagoon, which belongs to one of the largest hydrographic basins in the world, located in southern Brazil. Three distinct sampling periods were chosen (January, March, and June 2022) based on the rice plantation dynamics which is the main activity surrounding the lagoon. In January, the plantation is irrigated; in March, the water is drained into the Mirim Lagoon, and July is the off-season. Concerning toxicity tests, there was significant inhibition in microalgae growth when exposed to water collected in March, but no mortality was observed for Ceriodaphia dubia, Daphnia magna, and Danio rerio. Regarding biomarkers, behavioral variables contributed more to the higher values of the Integrated Biomarker Response (IBR) index for both D. magna and D. rerio, in March. The Redundancy Analysis (RDA) indicated a correlation between the biomarkers for both organisms and abiotic parameters, mainly nutrients (total phosphorus and total nitrogen), thermotolerant coliforms, total solids, and turbidity. Spatially, there was no difference during monitoring, but the most significant ecotoxicological effects were observed in March. Multivariate analysis and the IBR index proved to be useful tools for monitoring of water bodies such as Mirim Lagoon.

Paleoclimatic and paleoenvironmental significance of late Pleistocene pedogenic carbonates (‘Caliche Cordão’) from the coastal Pampa of southern Brazil

The pedogenic carbonates found in Pleistocene units of the coastal Brazilian Pampa, informally designated as ‘Caliche Cordão', include rhizocretions, soft masses and isolated or coalescent nodules, either isolated within the sediment or forming discrete horizons, the most developed horizons (Ca-01 and Ca-02) stretching for hundreds of meters along the banks of Chuy Creek. Petrographic analyses show micritic (Alpha-type) matrix in most samples, with few signs of recrystallization as circumgranular spar rims or cracked sand grains. Stable carbon (δ13C) and oxygen (δ18O) isotope values in samples from the lower horizon Ca-01 exhibit small variation and indicate C3-dominated plant assemblages and carbonate precipitation from relatively 18O-enriched water, whereas the δ13C and δ18O in samples from the upper horizon (Ca-02) exhibit wider variation, higher proportion of C4 plants and precipitation from 18O-depleted water in some samples. The δ18O variations can be explained by variable degrees of evaporative enrichment, or to relative contributions of 18O-depleted (tropical) or 18O-enriched (subtropical) rainfall, based on the similarity with estimates from fossils of mastodons. Nodules from other sites are similar, but larger isotopic variations indicate carbonate precipitation at distinct times and environmental conditions, and a few exhibit partial recrystallization as larger spar calcite crystals. Luminescence ages of ∼74.7 and ∼71.3 ka of quartz grains in two nodules from Ca-01 indicate precipitation during MIS 4, whereas ages of ∼52 ka from Ca-02, and ≥30 ka in nodules from the shores of Mirim Lagoon indicate carbonate formation between MIS 3 and MIS 2. The probable source of carbonate was calcium released from eolian-sourced silty dust produced by Andean glaciers and transported from loess deposits in Argentina during cold and dry intervals of the last glacial, when arid/semiarid environments expanded from Patagonia across the Pampas up to southern Brazil. The variations of δ13C in calcretes formed between MIS 4 and 2 point to changes in plant assemblages that could have contributed for the local extinction of the mammalian megafauna.

Hydromorphodynamics modeling of dredging and dumping activities in Mirim lagoon, RS, Brazil

This study aims to employ a combination of numerical models to simulate bed evolution under various operational strategies within two navigation channels in Mirim Lagoon, Brazil. The model simulations accurately represent the water levels within the lagoon. These findings suggest that river discharge plays a pivotal role in shaping the temporal patterns of sediment transport within the system. The morphodynamic model reveals that sediment transport and bed evolution primarily occur in a southwest-to-northeast direction, following the flow of water. The greatest sediment accumulation is observed in the central and southern regions of the lagoon. Our results confirm that channel dredging induces significant variations in lagoon physical parameters, such as current velocity. The bed evolution results indicate that rapid siltation of the channel follows dredging, suggesting a substantial increase in bottom evolution within the navigation channels compared to the unaltered scenario. Our findings highlight that the utilization of hydromorphodynamic modeling, with a particular emphasis on dredge-and-dump strategies, can serve as a precise methodology to enhance natural mechanisms that positively influence channel depth and stability. This approach also enables us to predict unfavorable changes in physical parameters over both the medium and long term.

Composition and diversity of fish assemblages along a shallow beach of a neotropical coastal lagoon

Coastal lagoons are inland water bodies connected to the sea and influenced by freshwater discharge, so these environments undergo constant changes in physical–chemical water characteristics. Transitional environments are important for promoting breeding, refuge, and food areas, besides serving as possible nursery habitats for fish species. In the present study, we analyzed the structure of the fish assemblages in a shallow marginal area of Mirim Lagoon, which belongs to the Laguna Estuarine System (LES), by seasonally evaluating the composition, structure, and diversity of the assemblages. Fieldwork was carried out between September 2017 and August 2018 with three monthly replicates using a beach seine net. Analyses were conducted to highlight the general patterns of the assemblages and to verify seasonal variations in composition, abundance, and diversity. The common species were defined using a species abundance curve, while the seasonal variation in diversity was evaluated using integrated rarefaction and extrapolation curves that correspond to the three orders of Hill numbers. The differences in the specific seasonal composition were indicated by dbRDA and the existence of statistical differences was tested using a PERMANOVA. In total, 3,556 individuals distributed in 16 families and 26 species were caught, with the predominance of Atherinella brasiliensis, Eucinostomus melanopterus, Coptodon rendalli, Eucinostomus argenteus, Mugi lliza, Anchoa tricolor, and Achirus lineatus that represented approximately 98% of the total. Regarding seasonality, the highest abundance was caught in the winter, while the lowest abundance was caught in autumn. The PERMANOVA indicated differences between spring and autumn and between autumn and winter. The main differences between these seasons are associated with the number of individuals caught, species abundance, and species composition. The presence of juveniles of several fish species, especially non-resident species, demonstrates the importance of the shallow area of Mirim Lagoon as a breeding, growth, and protection site that serves as a possible nursery habitat for these species.

Modelo preditivo para monitorar a turbidez da água em uma lagoa subtropical usando imagens MSI Sentinel-2A/B

ABSTRACT Ensuring prompt and effective water quality monitoring is increasingly important. Remote sensing has been shown to be an effective tool for simplifying and speeding up this process. The aim of this study is to develop an empirical model to map the spatial and temporal dynamics of turbidity in Mirim Lagoon, located in southern Brazil. To achieve this, Sentinel-2A/B MSI sensor data were combined with turbidity data collected in situ. The model was applied to monthly images (with cloud cover ≤ 20%) in 2019 and 2020 using the Google Earth Engine (GEE) platform. Mean turbidity values in the lagoon did not vary significantly, remaining between 30 and 75 NTU overall. However, there were differences in turbidity levels between the northern and southern regions of the lagoon in some months of the investigated years. By applying this methodology and analyzing the results, we were able to better understand the behavior of turbidity throughout the lagoon and gain insights into the quality of this important freshwater source.

Continuous discharge monitoring of the Mirim-São Gonçalo system by the index velocity rating curve method

Abstract The São Gonçalo Channel, located in the south of Brazil, is responsible for connecting the Mirim Lagoon to the Patos Lagoon, constituting the largest coastal lagoon system in Latin America. The assessment of its hydraulic variables is necessary given the importance of this channel for the region. Thus, this study aimed to evaluate the performance of the index velocity rating curve (IVRC) method, from velocity measurements provided by horizontal static-type acoustic Doppler profilers (H-ADCPs). For the two sections analyzed in this study (GS1 and GS2), IVRC models were developed considering the integrated velocity cell (IVC) method; the multi-cell velocity (MCV) method; the joint use of IVC and MCV; and a stage-mean velocity rating curve. The results point to an r2 of 0.986 (IVC), 0.998 (IVC + MCV), 0.534 (stage-mean velocity) at GS1, and r2 of 0.986 (IVC), 0.995 (IVC + MCV), and 0.815 (stage-mean velocity) at GS2. In both GS1 and GS2, results showed significant gains – for different flow conditions – on continuous estimations of flow velocities and discharges when considering the MCV + IVC method. The IVRC model that presented the best fit allowed the development of a time-series of discharges in the studied sites with high reliability.

Empirical and semi-empirical chlorophyll-a modeling for water quality assessment through river-lake transition in extreme Southern Brazil.

Mirim lagoon is the second largest lacustrine water body in Southern Brazil, providing water for local communities. However, algae growth and water quality in the lagoon and in tributaries rivers is influenced by nutrient's increase. In this context, this study performs the empirical and semi-empirical chlorophyll-a (Chl-a) modeling using remote sensing and in situ data for water quality assessment. Water quality data were collected at 15 sample locations in the lagoon on the date of Sentinel-2 satellite overpass. Surface reflectance data were derived from the Sen2Cor atmospheric correction method and correlated with Chl-a concentration. The best model presented a Pearson's correlation coefficient = 0.81 and Mean Absolute Error = 0.13µg.L-1. Low Chl-a concentration is observed at the Northern lagoon, possibly due to suspended solids presence. The same occurs in the left margin, being associated with the influence of land use for agriculture. High Chl-a concentrations are associated with shallower and lentic areas. The mean Chl-a concentration predicted by the model was 17.34μg.L-1, similar to the observed value in situ (16.32μg.L-1). Overall, the empirical model developed can be applied as a tool to reduce costs and efforts in fieldwork measures and to understand eutrophication in this river-lake transition ecosystem.

Analysis of the Influence of Water Quality Parameters in the Final WQI Result Through Statistical Correlation Methods: Mirim Lagoon, RS, Brazil, Case Study

Analysis of the Influence of Water Quality Parameters in the Final WQI Result Through Statistical Correlation Methods: Mirim Lagoon, RS, Brazil, Case Study

The effect of agricultural intensification and water-locking on the world's largest coastal lagoonal system

The palaeolimnological conditions of Mirim Lagoon, a large coastal shallow lagoon under the influence of historical human impacts related to the development of the primary sector of the economy were reconstructed. The first significant human impact consisted of locking the estuarine system to induce the transition from brackish to freshwater conditions. During this transition, the sedimentation rate consistently increased from pre-disturbance values of 0.25 cm yr−1 to >1 cm yr−1. A concomitant increase in nitrogen and carbon values was recorded indicating a related eutrophication process. The highest nutrient levels were achieved during the 1990s after the incorporation of cutting-edge technologies for agricultural production such as high-yielding varieties of rice resistant to climate variability and pests, and the use of inorganic fertilisers, pesticides and water supply controlled by irrigation. After 2011, the soybean production boosted and the area cultivated with this oilseed equalled the area of rice paddies, i.e., 2 × 105 ha. A sharp decrease in δ13C from −19 to −24‰ and in δ15N from 6 to 2‰ were observed in the sedimentary record, indicating a major shift in the composition of the organic matter after the agricultural intensification. Trace elements Cr, Cu, Ni and Zn showed a high positive correlation with Al and Fe, and enrichment factors near 1, indicating a natural and terrigenous source of these elements and also unpolluted conditions. However, the increase of As after 1990 and the positive correlation with Pb was associated with agricultural practices. All elemental ratios (K/Al, Ti/Al and V/Cr) showed constant pre-disturbance trends and a turning point ca. the 1990s. Microplastics were detected from the beginning of the 1990s and increased towards recent sediments, thus corroborating an anthropogenically impacted scenario. Therefore, the development of the primary sector of the economy exerted clear impacts on the environmental quality of the system.

Geomorphological and stratigraphic evolution of a fluvial incision in the coastal plain and inner continental shelf in southern Brazil

This paper describes the evolution of a sector of the southern coastal plain of the Pelotas Basin, southern Brazil, between the last Pleistocene sea-level lowstand and the Holocene highstand, based on geomorphology and high-resolution stratigraphy. A fluvial drainage system associated with an incised valley developed during the Last Glacial Maximum (LGM) was identified. Two high-resolution 2D and 2.5D geophysical profiles using Ground-Penetrating Radar (GPR) show a Pleistocene fluvial system's former path, starting close to its present mouth inside Mirim Lagoon crossing the coastal barriers and reaching the inner continental shelf, covering some 60 km across the coastal plain. During the LGM, with the sea-level at −120 to −130 m and the coastline positioned close to the shelf edge (distant 200 km from the present coastline), the fluvial system excavated a ~31.5-m deep channel. Two cores, 36 and 32 m long, show that the paleochannel was filled with sedimentary deposits after 19.4 ka BP, and the facies succession represents the transition from fluvial, to estuarine, to the coastal barrier, and finally to inner shelf depositional environments, generated by processes connected to LGM and the Postglacial Marine Transgression (PMT). The study region behaved as a sediment by-pass zone, connecting the adjacent coastal plain's inner portion with the inner continental shelf. The studied area presents an unusual record of the LGM at a coastal plain domain.

Assessment of the Water Quality of the Mirim Lagoon and the São Gonçalo Channel Through Qualitative Indices and Statistical Methods

The Mirim Lagoon is one of the most important freshwater lagoons in the Brazilian territory, connecting the Patos Lagoon through the Sao Goncalo Channel. With the diversification of the uses of rivers, watersheds, and lakes, sustainable management and management of these ecosystems are extremely relevant. For this reason, the monitoring of these environments is of great importance. In view of the above, the water quality index (WQI), the trophic state index (TSI), and statistical methods are tools that enable rapid assessment of water characteristics regarding pollution sources, expressing its quality in a single value, which facilitates understanding. Thus, this study aims to evaluate the water quality of the Mirim Lagoon and the Sao Goncalo Channel through these methods. With the proposed methods, it was possible to observe that the Mirim Lagoon and the Sao Goncalo Channel suffer strong influence from agricultural activities and the release of untreated effluents into their beds, causing the deterioration of these water resources. Despite this, for the most part, the collection points had a good WQI and TSI varying between quality ranges 1 and 3. Furthermore, the importance of statistical methods to assess the studied parameters is highlighted, since they promote more accurate results.

Organic carbon accumulation in oligotrophic coastal lakes in southern Brazil during the last century

We report organic carbon (OC) accumulation rates in three freshwater ecosystems in southern Brazil, along the largest shallow coastal lagoon ecosystem in the world, the Patos-Mirim-Mangueira. After European colonisation in the seventeenth century, regional wetlands started being replaced by agricultural fields (mostly rice). We used excess 210Pb to develop chronologies for lagoon sediment cores and quantify bulk sediment and OC accumulation rates. In the past 120 years, OC accumulation rates in Mirim and Mangueira Lagoons, which are influenced by rice paddies, averaged 14.9 ± 8.5 and 6.4 ± 3.7 g C m−2 year−1, respectively. Greater accumulation rates were estimated for macrophyte-dominated Nicola Lake (69.9 ± 38.5 g C m−2 year−1) located within the protected Taim Wetland with no direct influence of rice plantations. Starting in the early twentieth century, the construction of dams and drainage canals altered regional hydrology. Despite these anthropogenic changes, only a mild increase in OC accumulation was observed in Mirim Lagoon (15% only in site MIR2) after 1970. Mangueira Lagoon experienced the lowest OC burial rates despite increasing sedimentation rate and OC burial after the mid-1970s. This is probably because these large lakes (> 500 km2) have great nutrient-dilution potential, and their well-mixed water columns prevent nutrients from accumulating in the sediments over time.

Multiple linear regression analysis (MLR) applied for modeling a new WQI equation for monitoring the water quality of Mirim Lagoon, in the state of Rio Grande do Sul\u2014Brazil

Accurate assessment of the type and extent of water pollution is a difficult and complicated task. Therefore, the use of the Water Quality Index (WQI) proves to be a useful tool, as this index has the advantage of resulting in a single number that is easy to communicate and understand. One of the statistical methods that can be used to develop a new WQI equation for a given water body is Multiple Linear Regression (MLR). Therefore, this work aims to develop a new WQI equation for Mirim Lagoon through MLR and to evaluate the suitability of that equation. For this, 154 samples collected at 7 monitoring points of Mirim Lagoon over three years were analyzed, from which the original WQI results were obtained. With these results, MLR was applied, generating a new WQI equation with only three variables: phosphorus, dissolved oxygen (DO) and thermotolerant coliforms. This MLR model obtained an R2 coefficient equal to 0.728, demonstrating that 72.8% of the data variability was explained by the equation generated by this model. Through the paired t test it was possible to demonstrate that the results of the new WQI did not differ significantly from the results of the original WQI, obtaining significance values greater than 0.05 for both absolute WQI values and quality ranges (p value 0.886 and 0.467, respectively), attesting to the adequacy of the new equation. The reduction in the number of variables for monitoring water quality has several advantages, from financial ones, as it makes monitoring less costly, even in reducing the eclipse effect. Therefore, it is concluded that it is of great importance to generate an equation with fewer variables for monitoring the quality of the waters of Mirim Lagoon.

Technological Hazard Vulnerability: A GIS-Based Approach for Supporting Environmental Zoning.

Technological hazard assessments are extremely rare in Brazil, despite their importance for planning. Aquatic systems are of particular concern, since they are the endpoint of every process occurring in the watershed, including technological disasters. Thus, our goal is to map the technological hazard vulnerability in lagoon systems though a geographic information systems (GIS) model. The technological hazard vulnerability model consists of the spatial overlapping of technological pressure and fragility, having environmental systems as spatial units. The methodology was applied to the lagoon systems of the Rio Grande do Sul State, Southern Brazil, as a case study. The very high vulnerability of the Northern Guaíba Lake is due to the high concentration of technological infrastructures combined with high fragilities of wetland systems. In the Patos Lagoon Estuary, highly vulnerable systems consist mostly in shallow waters. The Mirim Lagoon was less vulnerable compared to other systems, due to a much smaller occurrence of elements of technological pressure. The proposed methodology allowed for the identification of environmental systems particularly vulnerable to technological hazards, where management efforts must be more intense. The results were used for the Ecological-Economic Zoning of the Rio Grande do Sul, as well as to revise the water quality framework of the Patos Lagoon estuary, currently underway. Integr Environ Assess Manag 2021;17:445-454. © 2020 SETAC.

Empirical modelling of suspended solids in a subtropical lagoon (Brazil) using linear spectral mixing algorithm

The Linear Spectral Mixing Model (LSMM) technique has been used in remote sensing applications and allows the estimation of the proportional contribution of different constituents in the pixel reflectance. Despite the great potential for vegetation and land cover studies, there are few studies examining the LSMM efficiency for optically complex inland waters. In addition, LSMM-derived images have shown a promising application in water quality mapping. In this context, Mirim lagoon (Brazil) presents seasonal variability of suspended solids (SS) influenced by sediment yield from tributaries and surrounding areas (e.g.: croplands). While negative impact on water quality makes relevant the SS mapping for management of this ecosystem, there is no studies using remote sensoing in this lagoon. This study develops an empirical model for SS concentration in the Northern Mirim lagoon using Sentinel-2 MSI images. The framework applies the linear spectral mixing algorithm in two MSI images and the empirical model was developed using the multiple linear regression. We validated the model performance using Monte Carlo simulation method. The mapping of SS was satisfactory in both images: the estimated concentrations are consistent with in-situ measurements. The results show that LSMM application supports the mapping of SS and its spatial distribution. Finally, this study is the first application of Sentinel-2 MSI images in the Mirim lagoon and the results present the potential of this empirical modelling for sediment mapping. The spatial information supports the local managers to understand the sources of degradation of water quality and protect this aquatic ecosystem.

Links between surface sediment composition, morphometry and hydrodynamics in a large shallow coastal lagoon

This study addresses the surface sediment composition and distribution in Mirim Lagoon, a large coastal shallow transboundary system located on the border of South Brazil and Uruguay, which is 3749 km2 and maximum depth is around 6 m, in relation to the hydrodynamic conditions evolved from predominant winds. Surface water currents in the marginal area displayed maximum speed values of 0.25 to 0.3 m s−1 flowing parallel to the coastline either under NE of SW wind predominance. The marginal zone, above the 6 m bathymetric contour comprise sandy sediments, indicating that under such a combination of bathymetric and hydrodynamic conditions, the resuspension of fine sediments is dominant. Lower surface current velocity observed in the central zone of the lagoon located below the 6 m isobath (i.e., 0.05 m s−1), together with an increase in the maximum width of the lagoon, promoted conditions for deposition of the clay sediment fraction. Therefore, the combined use of sedimentological and hydrodynamic data represents a useful tool to infer patterns of deposition and resuspension in coastal systems. Given the large size of the Mirim Lagoon and associated difficulties in sampling and monitoring the system, the information presented here is important for environmental management, and particularly for planning future paleolimnological research and set the coring stations on appropriate coordinates within the central region, where relatively calm conditions and dominance of clay sediments are observed.

Seasonal assessment of water quality parameters in Mirim Lagoon, Rio Grande do Sul State, Brazil.

This paper aimed at to evaluate the qualitative effects of climatic seasonality in a subtropical lagoon, using Discriminant Analysis, as well to identify the most sensitive and responsible parameters for these changes. The Mirim Lagoon watershed is one of the main transboundary basins in South America and is of great economic importance for the region because its waters are used for irrigation of rice fields and for the potable water supply to populations close to it, in this way, these uses may affect the quality of the basin waters. The data used in the study were provided and collected by the Mirim Lagoon Development Agency. Water quality parameters were selected in a five-year database and submitted to statistical tests that demonstrated their distinctions throughout the climatic seasons. The results showed that the parameters temperature, pH, dissolved oxygen, biochemical oxygen demand, total nitrogen and total phosphorus differ statically between the four climatic seasons. Were also identified four discriminative parameters between the seasons, being them dissolved oxygen, biochemical oxygen demand, total nitrogen and total phosphorus. In this way, it can be concluded that the seasonality mainly affects anthropogenic pollution sources such as agricultural activities and domestic discharges.

Relationships between Wind Effect, Hydrodynamics and Water Level in the World’s Largest Coastal Lagoonal System

The Patos-Mirim is the largest coastal limnological system of the world, located in southern Brazil and eastern Uruguay, which encompass over 500 km of coastline. The economical demand for the development of an international waterway brings the need for understanding the Mirim lagoon dynamics and ulterior discharge into Patos lagoon in view of establishing navigation conditions and sustainable development. In this sense, circulation and freshwater discharge dynamics were assessed by running the numerical model TELEMAC-3D for a one-year-long simulation. The model identified the wind direction and intensity as the main combined forcing modulating water circulation and transport between the northern and southern portions and conditioning the recirculation cell orientation. Predominant winds from the S-SW directions could generate adverse conditions for navigation because they would yield low water levels under northwards water transport, thus creating shallow regions for navigation. Under such conditions, the high freshwater discharge coming from the Mirim lagoon would be restricted, and the communication to the Patos lagoon would be sufficiently weakened to prevent navigation activities. Therefore, we recommend that the viability of planning and implementing an international waterway, involving the two countries (Brazil and Uruguay), must take into account wind conditions prior to setting navigation traffic and avoid economic losses.

Validating the vertical quality of SRTM digital elevation model of the Mirim Lagoon hydrographic basin

Abstract. This work is part of a research project that aims at the automatic determination of knickpoints and the assessment of morphometric and hypsometric parameters of Mirim Lagoon Hydrographic Basin, using Shuttle Radar Topography Mission digital elevation model (SRTM-DEM) and spatial analyses.The analysis of geomorphologic systems is done using computational treatment of data obtained by remote sensing, especially those obtained by SRTM. These data permit the elaboration of a topographic model for the Earth surface and provide a base for studies in several units of geomorphologic analyses (geomorphologic systems), such as hydrographic basins.The most usual technique for derivation of relief morphologic attributes is based on digital elevation models (DEMs) and digital hydrographic nets. Computational routines are applied on those data for acquisition of the hydrography and drainage anomalies. The DEMs and the hydrographic nets must have either morphologic or hydrologic consistency to validate the results obtained in the morphometric analyses.More specifically, this study aims at describing the method and related results regarding the validation of the vertical accuracy of SRTM-DEM through a kinematic positioning based on the Global Navigation Satellite System (GNSS), in the Mirim Lagoon Hydrographic Basin region. Mirim Lagoon Hydrographic Basin is as cross-border basin located on the Atlantic coast of South America, and covers an area of 58,407.78 km2, where 47% of this area is in Brazil and 53% in Uruguay.Several studies deal with the validation of Digital Elevation Models (DEMs) and SRTM data using different GNSS surveying methods and receivers. The innovation of this work is the methodology developed to achieve the suitable accuracy for the control points coordinates to validate the SRTM-DEM of Mirim Lagoon Hydrographic Basin. The study used the kinematic relative positioning method with a recording rate of 1 second and without reference stations for post-processing with the precise point positioning (PPP) method. This methodology allowed covering a large area with reference stations being very far from the surveyed region and with different geodetic reference systems (two countries).The methodology entails the GNSS data acquisition and post-processing, the transformation from geometric heights into orthometric heights, the SRTM-DEM mosaic, the extraction of homologous points in the SRTM-DEM and the statistical analyses for validating the model.The study used a GNSS receiver of dual-frequency with recording rate of 1 second to collect a total of 275,916 points with 3D coordinates. Those points were post-processed using the PPP method with the Canadian Spatial Reference System – Precise Point Positioning (CSRS-PPP), and the ellipsoidal height was converted into orthometric height through the software INTPT geoid. During this work, we used the geopotential model (EGM96) to transform height differences between two countries, Brazil and Uruguay.In order to obtain the SRTM-DEM we used 15 SRTM images, version 3, band C, with a spatial resolution of 1 arcsecond (approximately 30 m). These images were individually processed to obtain the Digital Elevation Model Hydrologically Consistent (DEMHC) and to treat the inconsistencies. Afterwards, we created a mosaic with the 15 images.In the statistical analysis we examined the magnitude of absolute errors in the SRTM data. These errors were named discrepancies between the SRTM heights and the heights of GNSS survey points. After the post-processing and the heights conversion, the GNSS survey points were considered accurate and used as a reference for SRTM-DEM validation. The goal of the statistical analysis was to verify if the absolute vertical precision of the DEM data exceeds 16 m, according to the precision specifications of the DEM SRTM.Results showed that the vertical mean absolute error of the SRTM-DEM vary from 0.07 m to ± 9.9 m with average of −0.28 m. This vertical accuracy is better than the absolute vertical accuracy value of ± 16 m published in the SRTM data specification and validates the SRTM-DEM. Besides that, even considering different slopes and different heights the statistics showed that SRTM-DEM could be validated, in spite of the results for lower and flat area were more accurate than the ones for a higher area with high slope.